Motional Ground State Cooling Outside the Lamb-Dicke Regime

TL;DR

This paper demonstrates effective three-dimensional motional ground state cooling of a single sodium atom in an optical tweezer using Raman sideband techniques, despite challenging conditions like large Lamb-Dicke parameters and high initial temperatures.

Contribution

It introduces a method for Raman sideband cooling outside the Lamb-Dicke regime, including high-order sideband addressing and rapid tweezer intensity modulation.

Findings

Achieved 93.5% ground state population after 53 ms of cooling

Successfully cooled in a large Lamb-Dicke parameter regime

Demonstrated ground state cooling without tight confinement or low initial temperature

Abstract

We report Raman sideband cooling of a single sodium atom to its three-dimensional motional ground state in an optical tweezer. Despite a large Lamb-Dicke parameter, high initial temperature, and large differential light shifts between the excited state and the ground state, we achieve a ground state population of $93.5(7)$% after $53$ ms of cooling. Our technique includes addressing high-order sidebands, where several motional quanta are removed by a single laser pulse, and fast modulation of the optical tweezer intensity. We demonstrate that Raman sideband cooling to the 3D motional ground state is possible, even without tight confinement and low initial temperature.